CN114656234B - Red mud/coal gangue-based cementing material road base layer formula and preparation process - Google Patents
Red mud/coal gangue-based cementing material road base layer formula and preparation process Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
- C04B28/142—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements containing synthetic or waste calcium sulfate cements
- C04B28/144—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements containing synthetic or waste calcium sulfate cements the synthetic calcium sulfate being a flue gas desulfurization product
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/0075—Uses not provided for elsewhere in C04B2111/00 for road construction
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Y02P40/00—Technologies relating to the processing of minerals
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Abstract
The invention belongs to the technical field of road base materials, and particularly relates to a red mud/coal gangue based cementing material road base formula and a preparation process thereof. The red mud/coal gangue-based cementing material road base formula is prepared from the following raw materials in parts by weight: 37 parts of high-activity red mud, 0-20 parts of slag, 0-20 parts of desulfurized gypsum, 40 parts of gangue coarse and fine aggregates, 3 parts of calcium-containing solid alkali activator and 20-22 parts of water, wherein the high-activity red mud is obtained by sequentially carrying out mechanical activation and thermal activation on the red mud. The invention can directly apply various solid waste materials of red mud, slag, desulfurized gypsum and coal gangue, which harm the environment and harm the human health, to the road base, and the formula can meet the requirement of the strength of the highway and the first-level highway base, replace the traditional cement stabilized macadam base and cement, reduce the influence of hydration heat on the cementing material and improve the crack resistance of the road base.
Description
Technical Field
The invention belongs to the technical field of road base materials, and particularly relates to a red mud/coal gangue based cementing material road base formula and a preparation process thereof.
Background
Along with the development of industrial productivity in China, more and more solid wastes are discharged, and the stacking of the solid wastes not only pollutes the environment and wastes the land, but also harms human health to a certain extent. But since part of the solid waste contains some active ingredients that have a positive effect on strength, it can be further processed and applied to the road base.
The coal gangue is solid waste generated in the processes of development, excavation, coal mining, coal washing and processing of coal mines, and is industrial waste with the largest annual discharge amount and accumulated inventory amount in China at present. A large amount of stockpiling of the coal gangue not only occupies a large amount of land, but also influences the ecological environment of the coal gangue, can generate spontaneous combustion under certain conditions, discharges harmful gases such as carbon dioxide, sulfur dioxide, smoke dust and the like, and pollutes the land and underground water under the action of rainwater washing. The application of the coal gangue to a road base instead of cement stabilized macadam is a problem researched by numerous scholars at present, but the mixing amount of the coal gangue is not high due to the lower strength of the coal gangue relative to natural macadam, and the problem of large amount of stockpiling of the coal gangue cannot be effectively solved.
The red mud is industrial waste mud discharged in the production process of alumina. It is statistical that every ton of alumina produced will be accompanied by the discharge of 1.0-1.8 tons of red mud. China is a big country for producing alumina, and a large amount of stockpiled red mud cannot be effectively utilized, so that not only is resource waste caused, but also land is polluted and human health is harmed. The red mud belongs to strong alkaline soil, the specific surface area of the red mud is large, the binding force is strong, and the red mud cannot be used in large quantities, the doping amount of the red mud is usually lower than 30% in the current research aiming at the red mud-based road base layer, and the red mud is not significant compared with the high-yield discharge of the red mud.
The invention patent application CN107129249A discloses a Bayer process red mud and coal gangue roadbed material and a preparation method thereof, but in the method disclosed in the patent application, although red mud is ground, the ground particle size is still large, and red mud cannot be effectively activated, and the shrinkage performance of the additive is poor due to the action of hydration heat of cement as the additive adopts cement. The patent application CN113087487A of the invention relates to a construction process for stabilizing a red mud coal gangue aggregate pavement base course by using carbide slag and fly ash, but in the method disclosed in the patent application, because cement is not used, the red mud doping amount is not high, and the maximum doping amount is only 15%.
In conclusion, at present, it is urgently needed to develop a road base material and a formula for realizing the application of high red mud content under the condition of completely replacing cement, and the requirement of the road base strength can be met.
Disclosure of Invention
The invention aims to provide a red mud/coal gangue-based cementing material road base layer formula and a preparation process thereof, which solve the problem that the prior art can still realize high-doping-amount application of red mud under the condition of completely replacing cement, reduce the hydration heat of the cement, realize the comprehensive utilization of the red mud and have remarkable social and economic benefits.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the red mud/coal gangue based cementing material road base course formula is prepared from the following raw materials in parts by weight:
37 parts of high-activity red mud, 0-20 parts of slag, 0-20 parts of desulfurized gypsum, 40 parts of coal gangue coarse and fine aggregates, 3 parts of calcium-containing solid alkali activator and 20-22 parts of water; wherein, the raw material (refers to all raw materials) contains (CaO + Na) 2 O) and (SiO) 2 +Al 2 O 3 ) The mass ratio of (C) is expressed as (CaO + Na) 2 O)/(SiO 2 +Al 2 O 3 )，(CaO+Na 2 O)/(SiO 2 +Al 2 O 3 ) Is 0.72-1.65.
Further, the preparation method of the high-activity red mud comprises the following steps:
(1) Physical activation: ball-milling the red mud to the fineness of less than 0.3mm to obtain red mud raw material;
(2) Thermal activation: taking the red mud raw material obtained in the step (1), heating the red mud raw material from room temperature to 850-900 ℃ at the heating rate of 5 ℃/min, and then preserving heat for 30-50 min to obtain the high-activity red mud.
Further, the red mud in the step (1) is Bayer process red mud.
Further, the slag is alkaline slag, wherein M is more than 1, M is the weight ratio of alkaline oxide to acid oxide in the slag, the slag is powdery, and the particle size is less than or equal to 75um.
Further, the desulfurized gypsum: the main component is calcium sulfate dihydrate CaSO 4 ·2H 2 O, the content is more than or equal to 93 percent, the powder is in a powder shape, and the particle size is less than or equal to 75um.
Further, the gangue coarse and fine aggregate is obtained by waste gangue through a back-impact crushing method, and the grading range of the gangue coarse and fine aggregate is as follows: the mesh size is 19mm, and the aggregate passing rate is 100%; the mesh size is 9.5mm, and the aggregate passing rate is 72-59%; the mesh size is 2.36mm, and the aggregate passing rate is 31-22%; the mesh size is 0.075mm, and the aggregate passing rate is 5-2%. The crushing value of the coarse and fine aggregate of the coal gangue is less than or equal to 22 percent, and the needle sheet content is less than or equal to 18 percent.
Further, the calcium-containing solid alkali activator is CaO, wherein the total content of effective CaO and MgO is not less than 85%, and undigested residue in the CaO is not more than 7% by the residue of a 5um round-hole sieve.
Preferably, the red mud/coal gangue based cementing material road base layer formula is prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali excitant and water are 37 parts, 0 part, 20 parts, 40 parts, 3 parts and 22 parts in sequence; wherein (CaO + Na) in the raw material 2 O)/(SiO 2 +Al 2 O 3 ) Is 1.65.
Preferably, the red mud/coal gangue based cementing material road base layer formula is prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 5 parts, 15 parts, 40 parts, 3 parts and 21.8 parts in sequence; wherein in the raw materials: (CaO+Na 2 O)/(SiO 2 +Al 2 O 3 ) Was 1.33.
Preferably, the red mud/coal gangue based cementing material road base layer formula is prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali excitant and water are 37 parts, 8 parts, 12 parts, 40 parts, 3 parts and 21.7 parts in sequence; wherein (CaO + Na) in the raw material 2 O)/(SiO 2 +Al 2 O 3 ) Is 1.21.
Preferably, the red mud/coal gangue based cementing material road base layer formula is prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali excitant and water are 37 parts, 12 parts, 8 parts, 40 parts, 3 parts and 21.5 parts in sequence; wherein (CaO + Na) in the raw material 2 O)/(SiO 2 +Al 2 O 3 ) Was 1.07.
Preferably, the red mud/coal gangue based cementing material road base layer formula is prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 15 parts, 5 parts, 40 parts, 3 parts and 21.2 parts in sequence; wherein (CaO + Na) in the raw material 2 O)/(SiO 2 +Al 2 O 3 ) Is 0.85.
Preferably, the red mud/coal gangue based cementing material road base layer formula is prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali excitant and water are 37 parts, 18 parts, 2 parts, 40 parts, 3 parts and 21.1 parts in sequence; wherein (CaO + Na) in the raw material 2 O)/(SiO 2 +Al 2 O 3 ) And was 0.79.
Preferably, the red mud/coal gangue based cementing material road base layer formula is prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali excitant and water are 37 parts, 20 parts, 0 part, 40 parts, 3 parts and 20.9 parts in sequence; wherein (CaO + Na) in the raw material 2 O)/(SiO 2 +Al 2 O 3 ) Is composed of0.72。
The invention also provides a preparation process of the red mud/coal gangue based cementing material, which comprises the following steps:
weighing the raw materials according to a formula, dry-mixing the high-activity red mud, the slag and the desulfurized gypsum by using a mixer, adding water for stirring after the dry-mixing is finished, adding the gangue coarse and fine aggregate and the calcium-containing solid alkali activator into the mixture for stirring after the mixture is stirred to a state without large particles or lumps, preparing a test piece after the mixture is uniformly stirred, demoulding the test piece by using a demoulding machine, and placing the test piece into a curing box with the curing temperature of 20 +/-2 ℃ and the humidity of 95% for curing to a corresponding age.
Compared with the prior art, the invention has the following advantages:
the invention can increase the doping amount of the red mud under the condition of completely replacing cement, and finally obtains the performances of excellent unconfined compressive strength of 7d and 28d by regulating and controlling the proportion of each raw material, thereby meeting the requirements of the base strength of expressways and first-class highways.
The invention adopts the high-activity red mud to replace cement, can effectively avoid the influence of cement hydration heat on the shrinkage and cracking of the road base, and simultaneously replaces natural broken stone with the coal gangue, thereby saving the production cost and avoiding the environmental pollution.
Drawings
FIG. 1: (left) is a test piece diagram of the red mud/coal gangue-based cementing material prepared in the embodiment of the invention; and (right) is an unconfined compressive strength test chart of the red mud/coal gangue based cementing material test piece prepared in the embodiment of the invention.
FIG. 2 is a flow chart of the preparation process of the red mud/coal gangue based cementing material of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be clearly and completely expressed by the following specific examples.
The following raw materials were used as follows: the red mud is Bayer process red mud from Shanxi Huaxing aluminum industry Limited company in Shanxi Xiaoyi City of Shanxi province; the slag is blast furnace slag generated after blast furnace ironmaking, is from Hengnuo purification plant of Zhengzhou city in Henan province, and has a particle size of less than or equal to 75um after screening; the coal gangue is from Shanxi plastic coal gangue power generation Limited liability company; the desulfurized gypsum is from Henan province, jiangyi City Yuanheng water purification material factory, and the particle size is less than or equal to 75um after screening; the calcium oxide is from Yingge mining company Limited in Yichun City Feng county of Jiangsu province.
The XRF (X-ray fluorescence spectroscopy) analysis of the main chemical component content of each raw material (red mud, slag, desulfurized gypsum, coal gangue, calcium oxide) gave the results shown in table 1:
TABLE 1
Note: 1) LOI refers to loss on ignition, i.e., the rate of mass loss before and after ignition.
2) This is not to be construed since some impurity components or oxides of very low composition may be present in the respective raw materials due to various factors.
3) Since each raw material contains CaO component, calcium oxide, which is one of the raw materials, is used as an alkali activator, and for the avoidance of doubt, the raw material calcium oxide is called a calcium-containing solid alkali activator.
In the following examples and some comparative examples, the red mud used is a highly reactive red mud, i.e., the red mud raw material is obtained by physical activation and thermal activation. The specific steps for preparing the high-activity red mud are as follows:
(1) Physical activation: ball-milling red mud to the fineness of less than 0.3mm to obtain a red mud raw material;
(2) Thermal activation: and (2) putting the red mud raw material obtained in the step (1) into a muffle furnace, heating the red mud raw material from room temperature to 850 ℃ at a heating rate of 5 ℃/min, and then preserving the heat for 30min to obtain the high-activity red mud.
It should be noted that: the activated red mud oxide will change. The physical activation is to increase the specific surface area, thereby forming defects on the particle surface and accelerating the soluble Al 2 O 3 、SiO 2 The dissolution is beneficial to the invasion of external ions so as to accelerate the chemical reaction speed; the thermal activation is to activate the original oxide byThe thermal activation mode enables the red mud to be separated from free water or combined water, the original aluminosilicate structure is changed into an unstable metastable state structure, and a large number of Si-O and Al-O bonds are broken to achieve the purpose of activation.
The coarse and fine aggregate of the coal gangue used in the following embodiments and comparative examples is obtained by crushing waste coal gangue by adopting an impact crusher, and the grading range of the coal gangue is as follows: the mesh size is 19mm, and the aggregate passing rate is 100%; the mesh size is 9.5mm, and the aggregate passing rate is 72-59%; the mesh size is 2.36mm, and the aggregate passing rate is 31-22%; the sieve mesh size is 0.075mm, and the aggregate passing rate is 5-2%. The crushing value of the gangue coarse aggregate is less than or equal to 22 percent, and the needle sheet content is less than or equal to 18 percent.
Example 1: preparation process of red mud/coal gangue based cementing material
592g of high-activity red mud, 0g of slag and 320g of desulfurized gypsum are accurately weighed, 352g of water is added after the dry-mixing and the uniform stirring, 48g of a calcium-containing solid alkali activator and 640g of gangue coarse and fine aggregates are added after the uniform stirring, a cylindrical test piece with the diameter-height ratio of 1.
Example 2: preparation process of red mud/coal gangue based cementing material
Accurately weighing 592g of high-activity red mud, 80g of slag and 240g of desulfurized gypsum, adding 350g of water after dry stirring, adding 48g of calcium-containing solid alkali activator and 640g of gangue coarse and fine aggregate after uniform stirring, preparing a cylindrical test piece with the diameter-height ratio of 1, namely 100 multiplied by 100mm, demoulding by a demoulding machine, and placing the test piece into a curing box with the curing temperature of 20 ℃ and the humidity of 95% to cure to a corresponding age after demoulding by a demoulding machine.
Example 3: preparation process of red mud/coal gangue based cementing material
592g of high-activity red mud, 128g of slag and 192g of desulfurized gypsum are accurately weighed, 347g of water is added after the dry mixing and the stirring are uniform, 48g of calcium-containing solid alkali activator and 640g of gangue coarse and fine aggregate are added after the stirring is uniform, a cylindrical test piece with the diameter-height ratio of 1.
Example 4: preparation process of red mud/coal gangue based cementing material
592g of high-activity red mud, 192g of slag and 128g of desulfurized gypsum are accurately weighed, after dry stirring and uniform stirring, 345g of water is added, after uniform stirring, 48g of calcium-containing solid alkali activator and 640g of gangue coarse and fine aggregate are added, after uniform stirring, a cylindrical test piece with the diameter-height ratio of 1.
Example 5: preparation process of red mud/coal gangue based cementing material
592g of high-activity red mud, 240g of slag and 80g of desulfurized gypsum are accurately weighed, 340g of water is added after dry stirring and uniform stirring, 48g of calcium-containing solid alkali activator and 640g of gangue coarse and fine aggregate are added after uniform stirring, a cylindrical test piece with the diameter-height ratio of 1.
Example 6: preparation process of red mud/coal gangue based cementing material
592g of high-activity red mud, 288g of slag and 32g of desulfurized gypsum are accurately weighed, 338g of water is added after dry-mixing and uniform stirring, 48g of calcium-containing solid alkali activator and 640g of gangue coarse and fine aggregate are added after uniform stirring, a cylindrical test piece with the diameter-height ratio of 1.
Example 7: preparation process of red mud/coal gangue based cementing material
592g of high-activity red mud, 320g of slag and 0g of desulfurized gypsum are accurately weighed, 335g of water is added after dry stirring and uniform stirring, 48g of calcium-containing solid alkali activator and 640g of gangue coarse and fine aggregate are added after uniform stirring, a cylindrical test piece with the diameter-height ratio of 1.
Comparative example 1: preparation process of red mud/coal gangue based cementing material
608g of high-activity red mud, 256g of slag and 80g of desulfurized gypsum are accurately weighed, 350g of water is added after dry-mixing and uniform stirring, 656g of coal gangue coarse and fine aggregates are added after uniform stirring, a cylindrical test piece with the diameter-height ratio of 1 and the diameter-height ratio of 100 multiplied by 100mm is manufactured after uniform stirring, and the test piece is placed into a curing box with the curing temperature of 20 ℃ and the humidity of 95% to be cured to the corresponding age after being demoulded by a demoulding machine.
Comparative example 2: preparation process of red mud/coal gangue based cementing material
Ball-milling red mud to the fineness of below 0.3mm to obtain red mud raw materials, accurately weighing 592g of the red mud raw materials, 240g of slag and 80g of desulfurized gypsum, uniformly stirring the red mud raw materials, adding 340g of water, uniformly stirring the mixture, adding 48g of a calcium-containing solid alkali activator, adding 640g of gangue coarse and fine aggregates, uniformly stirring the mixture to prepare a cylindrical test piece with the diameter-height ratio of 1, namely 100 multiplied by 100mm, demoulding the cylindrical test piece by a demoulding machine, and placing the cylindrical test piece into a curing box with the curing temperature of 20 ℃ and the humidity of 95% to cure the test piece to the corresponding age.
Comparative example 3: preparation process of red mud/coal gangue based cementing material
608g of high-activity red mud, 224g of slag and 64g of desulfurized gypsum are accurately weighed, 347g of water is added after the dry mixing and the uniform stirring, 48g of calcium-containing solid alkali activator is added after the uniform stirring, 656g of gangue coarse and fine aggregate is added, a cylindrical test piece with the diameter-height ratio of 1.
Comparative example 4: accurately weighing 70g of cement and 1750g of natural macadam, adding 96g of water after dry mixing, uniformly stirring, manufacturing a cylindrical test piece with the diameter-height ratio of 1: 100mm, demoulding by a demoulding machine, and placing the test piece into a curing box with the curing temperature of 20 ℃ and the humidity of 95% to cure the test piece to the corresponding age.
Comparative example 5: 87g of cement and 1750g of natural macadam are accurately weighed, 99g of water is added after the cement and the macadam are uniformly dry-mixed, a cylindrical test piece with the diameter-height ratio of 1 and the size of 100 multiplied by 100mm is manufactured after the uniform stirring, and the test piece is demoulded by a demould machine and then placed into a curing box with the curing temperature of 20 ℃ and the humidity of 95 percent to be cured to the corresponding age.
Comparative example 6: 105g of cement and 1750g of natural macadam are accurately weighed, 102g of water is added after the cement and the macadam are evenly dry-mixed, a cylindrical test piece with the diameter-height ratio of 1: 100mm is manufactured after the uniform stirring, and the test piece is placed into a curing box with the curing temperature of 20 ℃ and the humidity of 95% to be cured to the corresponding age after being demoulded by a demoulding machine.
The mass parts of the raw materials in the red mud/coal gangue-based cement materials prepared in the above examples 1 to 7 and comparative examples 1 to 3 are shown in table 2 below.
TABLE 2
| Starting materials | High-activity red mud | Slag of mine | Desulfurized gypsum | Water (I) | Calcium oxide | Coal gangue |
| Example 1 | 37 | 0 | 20 | 22 | 3 | 40 |
| Example 2 | 37 | 5 | 15 | 21.8 | 3 | 40 |
| Example 3 | 37 | 8 | 12 | 21.7 | 3 | 40 |
| Example 4 | 37 | 12 | 8 | 21.5 | 3 | 40 |
| Example 5 | 37 | 15 | 5 | 21.2 | 3 | 40 |
| Example 6 | 37 | 18 | 2 | 21.1 | 3 | 40 |
| Example 7 | 37 | 20 | 0 | 20.9 | 3 | 40 |
| Comparative example 1 | 38 | 16 | 5 | 21.9 | 0 | 41 |
| Comparative example 2 | 37 (Red mud raw material) | 15 | 5 | 21.2 | 3 | 40 |
| Comparative example 3 | 38 | 14 | 4 | 21.7 | 3 | 41 |
Note: 1) In the table, calcium oxide refers to raw material calcium oxide (solid alkali activator containing calcium), and does not refer to the CaO content in the raw material.
The CaO content and Na content in the raw materials used for preparing the red mud/coal gangue-based cementing material in the above examples 1 to 7 and comparative examples 1, 2 and 3 2 O content, siO 2 Content of Al 2 O 3 Content and (CaO + Na) 2 O)/(SiO 2 +Al 2 O 3 ) The following calculation was performed, wherein (CaO + Na) 2 O)/(SiO 2 +Al 2 O 3 ) Means (CaO + Na) 2 O) mass and (SiO) 2 +Al 2 O 3 ) The mass ratio of (a).
According to the content of CaO and Na in each raw material 2 O、SiO 2 、Al 2 O 3 The CaO content A and Na in the raw materials for preparing the red mud/coal gangue based cementing material are calculated according to the following formula 2 O content B, siO 2 Content of C and Al 2 O 3 The content D is calculated, and (CaO + Na) is calculated 2 O)/(SiO 2 +Al 2 O 3 ) The value of (3).
m 1 Mass m of red mud 2 Mass of slag, m 3 Mass m of desulfurized gypsum 4 Mass m of coal gangue 5 Means mass m of solid alkali activator containing calcium Water (W) Refers to the mass of water.
A represents the CaO content in the raw materials used for preparing the red mud/coal gangue-based cementing material.
B represents Na in raw materials for preparing the red mud/coal gangue based cementing material 2 And (4) the content of O.
C represents SiO in raw materials for preparing red mud/coal gangue-based cementing materials 2 And (4) content.
D represents Al in raw materials for preparing the red mud/coal gangue-based cementing material 2 O 3 And (4) content.
E represents (CaO + Na) in raw materials used for preparing the red mud/coal gangue-based cementing material 2 O)/(SiO 2 +Al 2 O 3 ) The value of the content.
13 specimens obtained in examples 1 to 7 and comparative examples 1 to 6 were subjected to unconfined compressive strength (7 d, 28 d) tests.
Unconfined compressive strength test instrument: the measurement accuracy of the universal tester is +/-1%, the loading rate is 1mm/min, and the maximum pressure P (N) when the test piece is damaged is recorded.
Unconfined compressive strength R C In newtons per square millimeter (MPa), the following formula is calculated:
The unconfined compressive strength (7 d, 28 d) test data for the 13 samples are shown in table 3:
TABLE 3
As can be seen from the data in the table 3, the red mud/coal gangue based cementing material provided by the invention meets the 7d unconfined compressive strength standard of a highway and a first-class highway in the JTG/T F20-2015 & ltroad pavement base layer construction technology rules & gt, under the extremely heavy and extra heavy traffic load grades, namely, the standard is not less than 5MPa. The examples and the comparative examples 4, 5 and 6 show that the red mud/coal gangue based cementing material provided by the invention replaces the traditional cement stabilized macadam foundation layer under the condition of ensuring the strength, saves the production cost, avoids the influence of the hydration heat of the cement on the shrinkage cracking of the cementing material, and improves the cracking resistance of the cementing material. According to the comparative example 1, under the condition that the calcium-containing solid alkali activator is not added, the unconfined compressive strength of the pavement is obviously reduced, and the requirements of some high-grade pavements cannot be met; as can be seen from the comparative example 2, the unconfined compressive strength of the red mud raw material which is not subjected to thermal activation treatment and is adopted in the red mud/coal gangue-based cementing material is obviously reduced compared with the unconfined compressive strength of the red mud raw material which is not subjected to thermal activation treatment and is adopted in the high-activity red mud; as can be seen from comparative example 3, the strength is reduced by increasing the doping amount of the red mud, and the fact that 37% of the red mud is the maximum doping amount of the red mud is proved.
In addition, the formula materials provided by the embodiment of the invention are all selected from industrial solid wastes, so that the utilization rate of the solid wastes is improved, the wastes are changed into valuable, the problems of environmental damage and land waste caused by industrial wastes are solved, the ecological environment is protected, and the method is worthy of popularization. And the preparation process is simple and convenient for construction.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that are within the spirit of the present invention are intended to be included therein.
Claims (18)
1. The red mud/coal gangue-based cementing material roadbed layer material is characterized by being prepared from the following raw materials in parts by weight:
37 parts of high-activity red mud, 0-20 parts of slag, 0-20 parts of desulfurized gypsum, 40 parts of coal gangue coarse and fine aggregates, 3 parts of calcium-containing solid alkali activator and 20-22 parts of water; the calcium-containing solid alkali activator is CaO;
the preparation method of the high-activity red mud comprises the following steps:
(1) Physical activation: ball-milling the red mud to the fineness of less than 0.3mm to obtain red mud raw material;
(2) Thermal activation: taking the red mud raw material obtained in the step (1), heating to 850-900 ℃, and then preserving heat for 30-50 min to obtain the high-activity red mud.
2. The red mud/coal gangue-based cementitious material roadbed material of claim 1, wherein the coal gangue coarse and fine aggregate is obtained from waste coal gangue by a backstroke crushing method, and the grading range of the coal gangue coarse and fine aggregate is as follows: the mesh size is 19mm, and the aggregate passing rate is 100%; the mesh size is 9.5mm, and the aggregate passing rate is 72% -59%; the mesh size is 2.36mm, and the aggregate passing rate is 31% -22%; the sieve mesh size is 0.075mm, and the aggregate passing rate is 5% -2%.
3. The red mud/coal gangue based cementitious material roadbed material of claim 1, wherein the crushing value of the coal gangue coarse and fine aggregate is less than or equal to 22%, and the needle sheet content is less than or equal to 18%.
4. The red mud/coal gangue based cementitious material roadbed material of claim 1, wherein the slag is alkaline slag, wherein M is greater than 1, the M is the weight ratio of alkaline oxide and acidic oxide in the slag, the slag is in the form of powder, and the particle size is less than or equal to 75um.
5. The red mud/coal gangue-based cementitious material roadbed material of claim 1, wherein the desulfurized gypsum: the main component is calcium sulfate dihydrate, the content of which is more than or equal to 93 percent, the calcium sulfate dihydrate is powdery, and the particle size is less than or equal to 75um.
6. The red mud/coal gangue based cementitious material roadbed material of claim 1, wherein the effective content of CaO and MgO in the calcium-containing solid alkali activator is not less than 85%, and undigested residue in CaO is not more than 7% by sieve residue statistics of a 5um round hole sieve.
7. The red mud/coal gangue-based cementitious material roadbed material of claim 1, wherein in step (2) the red mud raw material is heated from room temperature to 850 ℃ at a heating rate of 5 ℃/min and is kept at the temperature for 30min.
8. The red mud/coal gangue-based cementitious material roadbed material of claim 1, wherein the red mud in step (1) is Bayer process red mud.
9. The red mud/coal gangue-based cementitious material roadbed material of claim 1, characterized in that the raw material comprises
And with
The mass ratio of (A) to (B) is recorded as
/
The above-mentioned
/
Is 0.72-1.65.
10. The red mud/coal gangue based cementitious material roadbed material according to any one of claims 1-9, which is characterized by being prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 0 part, 20 parts, 40 parts, 3 parts and 22 parts in sequence.
11. The red mud/coal gangue-based cementitious material roadbed material of any one of claims 1 to 9, which is characterized by being prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali excitant and water are 37 parts, 5 parts, 15 parts, 40 parts, 3 parts and 21.8 parts in sequence.
12. The red mud/coal gangue based cementitious material roadbed material according to any one of claims 1-9, which is characterized by being prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 8 parts, 12 parts, 40 parts, 3 parts and 21.7 parts in sequence.
13. The red mud/coal gangue based cementitious material roadbed material according to any one of claims 1-9, which is characterized by being prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 12 parts, 8 parts, 40 parts, 3 parts and 21.5 parts in sequence.
14. The red mud/coal gangue-based cementitious material roadbed material of any one of claims 1 to 9, which is characterized by being prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 15 parts, 5 parts, 40 parts, 3 parts and 21.2 parts in sequence.
15. The red mud/coal gangue-based cementitious material roadbed material of any one of claims 1 to 9, which is characterized by being prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 18 parts, 2 parts, 40 parts, 3 parts and 21.1 parts in sequence.
16. The red mud/coal gangue based cementitious material roadbed material according to any one of claims 1-9, which is characterized by being prepared from the following raw materials in parts by weight: the high-activity red mud, slag, desulfurized gypsum, gangue coarse and fine aggregates, calcium-containing solid alkali activator and water are 37 parts, 20 parts, 0 part, 40 parts, 3 parts and 20.9 parts in sequence.
17. The process for preparing the red mud/coal gangue based cementitious material roadbed material according to any of the claims 1-16, characterized in that the process comprises the following steps:
weighing the raw materials according to the formula, firstly dry-mixing the high-activity red mud, the slag and the desulfurized gypsum by using a mixer, adding water for stirring after the dry-mixing is finished, adding the gangue coarse and fine aggregates and the calcium-containing solid alkali activator into the mixture for stirring after the mixture is stirred to a state without large particles or lumps, and curing and solidifying the mixture to a corresponding age after the mixture is uniformly stirred.
18. The process according to claim 17, wherein the curing temperature is 20 ± 2 ℃ and the humidity is 95%.
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